CAREER: Mantle Hybridization via Melt-Rock Reaction-Implications for Chemical Variability of Oceanic Basalts and Lithologic Heterogeneities in the Earth's Convecting Mantle

事业：通过熔岩反应进行地幔杂交——对大洋玄武岩化学变异性和地球对流地幔岩性不均匀性的影响

• 批准号: 1255391
• 负责人: Rajdeep Dasgupta
• 金额: $ 63.58万
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-03-15 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1255391&HistoricalAwards=false
• 关键词: CAREER; Mantle; Hybridization; via; Melt

The research component in this CAREER award will focus on a series of experimental investigations of melt-rock reaction in Earth's heterogeneous upper mantle conditions. Partial melting of the Earth's upper mantle comprising peridotite and recycled crustal lithologies influences the thermal evolution of the planet, geochemical variability of the crust, differentiation of the interior, fluxes of key volatiles to the exosphere, and geophysical properties of the mantle. While isotopic and trace element geochemistry of erupted basalts have long-established the presence of subducted mid-ocean ridge basaltic (MORB) crust and continental sediment at mantle source regions of ocean island basalts (OIB), the identities of plausible lithologic heterogeneities and how such lithologies impart major element signatures on erupted lavas remain unresolved. Experiments thus far have mostly considered direct partial melting of various lithologies and not the reactive processes involving crust-mantle systems that should be ubiquitous in the convecting mantle. This experimental study will explore how subducted crustal lithologies-derived partial melts and peridotite reaction may produce a wide array of magma compositions and hybrid lithologies. These experiments will be conducted with the aid of piston cylinder (PC) and multi anvil (MA) devices, in order to constrain mantle hybridization via (1) MORB-eclogite-derived partial melts and fertile and depleted peridotite reaction, (2) metapelite-derived partial melts and peridotite reaction, and (3) partial melting of end member hybrid lithologies (modally altered peridotite and pyroxenites) produced by MORB/metapelite melt-peridotite interactions. Experiments are expected to span pressures and temperatures over which subducted crusts and sediments are partially molten but peridotite is unmolten. Major element compositions of reacted partial melts and reacted mineral assemblages will be determined as a function of depth, temperature, original crustal melt and peridotite compositions, extent of partial reactive crystallization, and melt-rock ratio. Furthermore, using high precision electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry, fractionation of elements such as first-row transition metals, Gallium, and Germanium will be determined with the goal of using these elements, in conjunction with major element equilibria, to constrain the mineralogic and lithologic heterogeneities of the basalt source regions.This CAREER project integrates the PI's Earth science research and teaching through a range of educational outreach activities, professional and career developments of students, and contributions to the broad field of earth science research. The proposed experiments will generate key data relevant to a wide range of Earth science disciplines including petrology-geochemistry, mineral physics, geodynamics, and seismology. The outreach activities will include a 10-week summer internship for one local community college student typically from underrepresented and minority groups, each year, in the PI's experimental petrology lab and supporting one high school or middle school teacher every year for a 4-week lesson plans development on solid Earth topics and research experience in the experimental lab. These two outreach activities are in line with the mission of and organized in collaboration with School Science and Technology (SST) Programs of Rice University. In addition, contents and visuals depicting the motivation, concepts, results, and implications of the proposed research will be developed by the PI for the 'Teaching Petrology in the 21st Century' website, an open-access resource widely used by petrology instructors for both undergraduate and graduate curriculum across the globe. The research performed as part of this proposal will facilitate operation of a new MA lab and will thus contribute towards collection of new MA pressure calibration and assembly data to be shared with the COMPRES (Consortium for Materials Properties Research in Earth Sciences). The generated experimental data on crust-mantle hybridization (with or without volatiles) will contribute towards newer generation thermodynamic, mineral physics, and geodynamic models of mantle materials and processes. Finally, with partial support from Rice, it is planned to engage two PhD students and recruit as many as five Rice undergraduates in order to advance their academic journey and educational experiences.

这一职业奖的研究部分将集中在地球上地幔不均匀条件下熔岩反应的一系列实验研究上。由橄榄岩和再循环地壳岩性组成的地球上地幔的部分熔融影响着地球的热演化、地壳的地球化学变异性、内部的分化、关键挥发分到外圈的通量以及地幔的地球物理性质。虽然喷发玄武岩的同位素和微量元素地球化学早已证实大洋中脊玄武岩(MORB)地壳和洋岛玄武岩(OIB)地幔源区存在大陆沉积，但可能的岩性不均质性的身份以及这种岩性如何赋予喷发熔岩的主要元素特征仍未得到解决。到目前为止，实验大多考虑了各种岩性的直接部分熔融，而不是涉及壳-地幔系统的反应过程，而壳-地幔系统应该是在对流地幔中普遍存在的。这项实验研究将探索俯冲地壳岩性衍生的部分熔体和橄榄岩反应如何产生广泛的岩浆成分和混合岩性。这些实验将借助活塞柱(PC)和多砧(MA)设备进行，以便通过(1)来自MORB榴辉岩的部分熔体和可育的和亏损的橄榄岩反应，(2)来自变质岩的部分熔体和橄榄岩反应，以及(3)由MORB/变质橄榄岩熔体-橄榄岩相互作用产生的端元混合岩性(模变橄榄岩和辉石岩)的部分熔融，以限制地幔杂交。预计实验将跨越压力和温度，在这些压力和温度范围内，俯冲地壳和沉积物部分熔化，但橄榄岩不熔化。反应部分熔体和反应矿物组合的主要元素组成将被确定为深度、温度、原始地壳熔体和橄榄岩成分、部分反应结晶程度和熔岩比的函数。此外，使用高精度电子探针显微分析和激光烧蚀电感耦合等离子体质谱，将确定第一排过渡金属、镓和锗等元素的分馏，目的是利用这些元素，结合主要元素平衡，限制玄武岩源区的矿物学和岩性不均一性。这一职业项目通过一系列教育推广活动、学生的专业和职业发展以及对广泛的地球科学研究领域的贡献，将PI的地球科学研究和教学整合在一起。拟议的实验将产生与广泛的地球科学学科相关的关键数据，包括岩石学-地球化学、矿物物理学、地球动力学和地震学。外展活动将包括每年为一名通常来自代表不足和少数族裔群体的当地社区大学生在PI的实验岩石学实验室进行为期10周的暑期实习，以及每年支持一名高中或中学教师参加为期4周的课程计划，内容涉及固体地球主题的发展和实验实验室的研究经验。这两项外展活动符合莱斯大学学校科学与技术(SST)项目的使命，并与其合作组织。此外，国际岩石学协会将为“21世纪的岩石学教学”网站开发内容和图像，描述拟议研究的动机、概念、结果和影响，这是一个开放获取的资源，被岩石学教师广泛用于全球的本科生和研究生课程。作为这项建议的一部分进行的研究将促进一个新的MA实验室的运作，从而有助于收集新的MA压力校准和组装数据，并与COMPRES(地球科学材料特性研究联合会)共享。所产生的壳幔杂化(含或不含挥发分)实验数据将有助于建立新一代地幔物质和过程的热力学、矿物物理和地球动力学模型。最后，在莱斯的部分支持下，计划招收两名博士生，并招收多达五名莱斯本科生，以推进他们的学术旅程和教育经历。